Catalyst composites which are utilized for the conversion of gases into useable products such as in the synthesis of methanol or water-gas shift reactions have comprised mixtures of copper, zinc and aluminum. However, a major problem which is associated with the use of these catalysts in the aforesaid reactions lies in their high sensitivity to poisons such as sulfur and chlorine. The sulfur and chlorine are usually present in the gaseous feedstocks which are utilized to effect the reaction, such gaseous feedstocks being derived from natural gas, the gasification of coal or the by-products from the refining of heavy oil, said gases being generally referred to as synthetic gases. In order to effectively utilize these catalysts in commercial operations, it is necessary that sulfur and chlorine guard beds be employed in order to reduce the level of the sulfur and chlorine to a range of about 10 parts ber billion (ppb).
The removal of these poisons such as sulfur is required due to the high affinity of the zinc component of the catalyst composite for sulfur, said affinity causing structural composition changes that lead to deactivation. Due to the high affinity of the metals for the poisons such as sulfur or chlorine, a build-up of the poison on the surface of the active metals will lead to the aforesaid deactivation of the catalyst. In view of this, it is therefore desirable to enhance the stability of the catalyst when utilizing such catalyst in a continuous commercial operation whereby the life of the catalyst is substantially lengthened or enhanced to a point where it is commercially feasible to operate the desired process. The stability and activity of the catalyst may be enhanced by the addition of certain components to the catalyst system whereby higher sulfur levels in the feedstock may be accommodated without requiring the presence of the aforesaid sulfur or chlorine guard beds, thus simplifying the overall design plan of the reaction process with a concurrent lower expense to operate the reaction process and obtain the desired product.
As will hereinafter be shown in greater detail, by employing the novel catalyst system of the present invention, it is possible to obtain results of high catalyst activity and more extensive stability of the same.